Research On Flow Characteristics For Axial-flow Reactor Coolant Pump With High-temperature Liquid Heavy Metal Medium

With the gradual maturity of the third-generation nuclear power technology independently developed by my country,the research and development of the more advanced fourth-generation nuclear power technology has entered a critical period.Among them,lead-cooled fast reactors represented by lead/lead-bismuth high-temperature liquid metal coolants are the future advanced nuclear power technologies that are being actively promoted by the world’s nuclear powers.The nuclear main pump is the only power source in the reactor,and its operational reliability is directly related to the safety of the nuclear power plant.The development of a lead-bismuth circulating main pump that meets the performance requirements is one of the key issues in the development of lead-cooled fast reactors.Taking Russia’s small modular lead-bismuth fast reactor SVBR-75 as an example,its main circulating pump adopts an axial-flow structure,and the fast reactor is designed to have a service life of 60 years,which means that the main pump must maintain a good working life in a relatively long operation period.The working condition is extremely demanding on the performance of the main pump.Mastering the flow characteristics of high-temperature liquid heavy metal media in the axial-flow nuclear main pump is one of the key issues in the design of lead-bismuth fast reactors.However,the current theoretical design and hydraulic performance tests of the pump are based on clear water media.When used in high-temperature liquid heavy metal media,it will inevitably lead to significant differences between the performance of the main pump and the design goals and hydraulic performance.In this study,the lead-bismuth medium was taken as an example,the axial-flow nuclear main pump was the research object,and the flow differences between the lead-bismuth medium and the clear water medium in the axial-flow nuclear main pump were compared.influence.The relevant research results have certain theoretical significance and application value for the independent research and development of lead-bismuth fast reactor equipment in my country.The main research contents and results are as follows:（1）Numerical simulation calculations were carried out for the axial-flow nuclear main pump in lead-bismuth medium and clear water medium respectively by numerical simulation method.The external characteristic curves of lift,efficiency and shaft power of the two media in the main pump operating range are obtained.Compared with the rated operating point,the lift of the main pump in the LBE medium is 3.5%higher than that of the clean water medium,and the efficiency is increased by 3.1%,and the ratio of the shaft power is equal to the ratio of the density of the two media.The working force has nothing to do with the medium.The reason for the performance change of the main pump is that the hydraulic loss of the LBE medium is smaller than that of the clean water medium.According to the theory of cylindrical layer independence of axial flow pump,comparing the flow of two media in the cylindrical layer with different radial coefficients,the flow difference is mainly concentrated in the hub and the rim position.At the outlet of the impeller,the circumferential component（Vu₂）of the absolute velocity of the LBE medium is significantly larger than that of the clean water medium,which causes its lift to be higher than that of the clean water medium.The head of the LBE medium in the impeller calculation domain is higher than that of the clean water medium,and the conversion ability of dynamic pressure to static pressure in the guide vane calculation domain is stronger than that of the clean water medium.（2）When comparing the two mediums flowing near the impeller and guide vane walls,it is found that the flow state of the LBE medium at the hub is significantly better than that of the clean water medium,which indicates that its flow ability against adverse pressure gradients is stronger than that of the clean water medium.The Reynolds number of the LBE medium is 5 times that of the clean water medium,which indicates that the inertial force of the LBE medium accounts for a larger proportion in the motion than that of the clean water medium.Comparing the distribution of shear stress coefficients of the two media on the impeller and guide vane walls,the shear stress coefficient of the LBE medium is smaller than that of the clean water medium,and its resistance in flow is smaller than that of the clean water medium,and the LBE medium is easier to maintain its motion state.（3）The flow of the two media at the tip clearance belongs to high pressure-low pressure flow.The Omega vortex identification method is used to extract the tip leakage vortex structure of the two media,compare the movement trajectory and flow field characteristics of the leakage vortex,and analyze the flow characteristics of different media at the tip of the blade.Differences in leak flow.The leakage distance of the leakage vortex of the LBE medium is greater than that of the clean water medium,and its pressure pulsation amplitude in the blade tip clearance is also greater than that of the clean water medium.